New Study Warns Carney’s Retaliatory Tariffs Against Trump Risk Undermining U.S. Legal Challenges

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Trade wars are usually fought at border crossings, but Canada’s latest confrontation with the United States could also be decided in an American courtroom.

A new economic study warns that Prime Minister Mark Carney’s retaliatory tariffs against Donald Trump could unintentionally strengthen the legal defence of the very U.S. tariffs Ottawa wants eliminated. The concern centres on a rarely used American trade law that allows Washington to punish countries accused of discriminating against U.S. commerce.

With billions of dollars in cross-border trade affected, the warning raises an uncomfortable question for Ottawa: Could fighting back against Trump’s tariffs make it harder for American businesses and legal experts to overturn them?

A New Economic Study Raises Concerns About Canada’s Strategy

The Montreal Economic Institute (MEI) issued a warning on October 8, 2026, arguing that Canada’s dollar-for-dollar retaliation against American tariffs could undermine legal efforts inside the United States. The economic note, prepared by senior fellow Phillip W. Magness in collaboration with policy analyst Gabriel Giguère, questions whether Ottawa’s response is serving Canada’s long-term interests. Although retaliatory tariffs demonstrate political resolve, the researchers argue they may also give Trump’s lawyers additional arguments to defend the administration’s trade restrictions.

The concern is particularly significant because American courts have already rejected some of Trump’s earlier tariff measures. Rather than relying entirely on political negotiations, Canadian businesses could benefit from successful legal challenges brought by American importers. The MEI argues that Canada should avoid making those challenges more difficult. Its warning does not mean retaliatory tariffs automatically become unlawful or that Trump’s tariffs are legally justified. Instead, it identifies a potential weakness in one argument opponents could use against Washington’s latest measures.

Trump Has Revived a Trade Law Dating Back to 1930

At the centre of the dispute is Section 338 of the U.S. Tariff Act of 1930, part of the legislation commonly known as the Smoot-Hawley Tariff Act. The provision allows an American president to impose additional duties of up to 50% on goods from countries found to discriminate against U.S. commerce. Although the statute remained on the books for decades, Trump’s administration became the first to expressly invoke it to impose tariffs. Its application has therefore raised significant questions about how modern American courts should interpret a law written nearly a century ago.

Trump invoked Section 338 in July 2026, alleging discriminatory Canadian practices involving dairy products, alcoholic beverages and motor vehicles. After a brief postponement, the resulting tariffs took effect on August 22, affecting approximately US$20 billion worth of Canadian products. The unusual legal foundation matters because Washington must defend its actions under the authority Congress actually granted. If the administration cannot establish the required discriminatory treatment, or if newer trade laws have displaced Section 338, the tariffs could face serious legal difficulties.

Two Legal Arguments Could Threaten Trump’s Latest Tariffs

The MEI identifies two potential arguments against Trump’s use of Section 338. The first concerns whether the 1930 provision remains available in its original form. Congress subsequently passed the Trade Expansion Act of 1962 and the Trade Act of 1974, establishing additional rules and procedures governing presidential trade actions. Under Section 301 of the 1974 legislation, the U.S. Trade Representative generally operates through a structured process for investigating unfair foreign trade practices. Researchers argue that relying on Section 338 could allow the administration to bypass safeguards established by those later laws.

The second argument focuses on whether Canada actually engaged in the discrimination necessary to justify the tariffs. This is where Ottawa’s retaliation becomes particularly sensitive. Canadian counter-tariffs deliberately apply additional charges to selected American products, potentially making Washington’s allegations easier to defend. However, the first legal argument would remain available even if a court accepted that discriminatory restrictions existed. The researchers’ position is therefore not that Canada’s retaliation guarantees Trump a courtroom victory, but that it could weaken one important line of attack.

The Timing of Canada’s Retaliation Could Be Crucial

An important detail complicates the argument that Carney’s retaliation strengthens Trump’s legal position: the chronology. Trump announced the Section 338 measures on July 20, and the new American tariffs took effect on August 22. Canada’s latest dollar-for-dollar counter-tariffs did not begin until September 8. That sequence creates a potential argument for challengers, who could contend that restrictions introduced after the original American decisions cannot automatically justify findings made weeks earlier. A court would need to examine the relevant statutory requirements and the evidence available when the measures were adopted.

However, Canada’s trade restrictions did not begin in September. Ottawa had already imposed retaliatory measures affecting American automobiles, while several provinces had restricted U.S. alcohol sales or purchases. Washington also raised objections to Canada’s longstanding dairy-market protections. These earlier measures could form part of the administration’s defence, independently of the latest retaliation. The distinction became even more important when Trump announced additional product restrictions in September, including import prohibitions that took effect on September 29. The timing and legal basis of each action could become central to future litigation.

The U.S. Supreme Court Has Already Rejected Part of Trump’s Tariff Strategy

The warning carries additional weight because Trump’s trade policies have already suffered a major legal defeat. On February 20, 2026, the U.S. Supreme Court ruled that the International Emergency Economic Powers Act did not authorize the president to impose tariffs. The decision invalidated a central component of Trump’s earlier trade strategy and put more than US$175 billion in collected tariff revenue at risk of refunds, according to estimates from the Penn Wharton Budget Model. For American companies that had paid substantial import duties, the ruling demonstrated that presidential trade actions could be successfully challenged.

Trump’s administration subsequently pursued other legal authorities, including Sections 122, 301 and 338 of different trade statutes. In May, the U.S. Court of International Trade also rejected certain tariffs imposed under Section 122, although that decision was stayed during the appeals process. These developments help explain the MEI’s focus on American litigation. However, the Supreme Court’s ruling concerning emergency powers does not automatically invalidate tariffs imposed under Section 338. Each provision grants different powers and carries separate legal requirements, leaving the latest Canada-specific restrictions subject to their own judicial examination.

Canada’s Counter-Tariffs Cover Billions in American Products

Ottawa’s retaliation represents a substantial expansion of the trade confrontation. Effective September 8, Canada introduced additional tariffs of 15%, 25% and 50% on selected American goods, covering approximately C$27.6 billion in U.S. imports. The affected categories include steel, aluminum, dairy products, household appliances, agricultural equipment, paper products and electronics. According to the federal government, the measures were designed to match American restrictions and provide Canadian manufacturers with a more competitive position against U.S. suppliers. Existing countermeasures on American automobiles also remained in place.

The consequences extend beyond government negotiations. Canadian companies importing machinery, equipment or consumer products from the United States can face higher purchasing costs, particularly when suitable domestic alternatives are unavailable. Some businesses may absorb those expenses, while others could pass them along to customers. Ottawa has also announced a C$7.5 billion package of new and enhanced support measures for affected workers and businesses, including financing and employment assistance. The combination illustrates the trade-off: Canada is attempting to protect domestic industries while managing additional costs created by its own retaliatory restrictions

Disputes Over Dairy, Alcohol and Automobiles Complicate the Legal Picture

Washington’s complaints involve three industries with very different trade arrangements. The Trump administration argues that Canadian provincial restrictions unfairly target American alcoholic beverages, that Canada’s retaliatory auto duties disadvantage U.S. manufacturers, and that Canadian dairy import-quota rules provide unequal opportunities to American suppliers compared with European competitors. These claims appeared in the presidential proclamations issued in July. However, establishing that a trade restriction exists is not necessarily the same as demonstrating that it justifies the particular tariffs imposed under Section 338.

Canada’s dairy system illustrates that complexity. The United States negotiated market-access provisions under CUSMA, including tariff-rate quotas that allow specified quantities of American dairy products to enter Canada at preferential rates. A dispute panel ruled against Canada on certain quota-allocation practices in 2021, while another panel sided with Canada in a separate case in 2023. The automotive dispute is similarly complicated by deeply integrated supply chains. Congressional research shows Canada purchased approximately US$61 billion in American automotive products in 2025, representing 38% of U.S. automotive exports. These relationships make sweeping trade restrictions potentially costly for businesses on both sides of the border.

Carney’s Government Says Retaliation Is Necessary to Protect Canadian Interests

The MEI’s warning challenges an approach Ottawa considers essential to defending its economic interests. When Carney suspended trade negotiations in August, he argued that Washington had introduced demands Canada could not reasonably accept. His government maintained that any agreement must preserve Canadian sovereignty, protect major industries and provide predictable access to American markets. From Ottawa’s perspective, accepting substantial new tariffs without responding could weaken its negotiating position and leave Canadian manufacturers competing against American products under increasingly unequal conditions.

Carney has also acknowledged the costs of retaliation. In his August 22 remarks, he recognized that Canadian counter-tariffs would increase prices and reduce consumer choice. The government nevertheless considers the measures justified because it believes the alternative would expose domestic businesses to greater long-term risks. Importantly, Carney also indicated that Canada had been prepared to remove certain retaliatory tariffs if Washington substantially reduced its restrictions on strategic sectors. That position suggests Ottawa views retaliation as negotiable economic leverage rather than a permanent objective. The central disagreement with the MEI concerns whether that leverage outweighs the possible legal and economic disadvantages.

Public Opinion Creates Pressure on Both Sides of the Border

Retaliation remains popular in Canada despite its economic costs. An Ipsos poll released on August 29 found that 73% of Canadians supported dollar-for-dollar tariffs on the United States. Across the border, an Economist/YouGov poll conducted August 28–31 found 58% of Americans opposed raising tariffs on Canadian goods, while 26% supported the idea. The same survey found 68% believed Trump’s tariffs had hurt ordinary Americans. Those results suggest Ottawa does not face a uniformly hostile American public, even as the Trump administration continues defending its trade restrictions.

The economic concerns behind those numbers are especially visible in Michigan, where automotive supply chains stretch across the international border. On October 7, Republican U.S. Senate candidate Mike Rogers, who had previously defended Trump’s tariffs, called for ending the trade confrontation in a campaign advertisement filmed at a neighbourhood bar, with a bottle of Canadian beer in hand. His Democratic opponent, Abdul El-Sayed, criticized the reversal as politically motivated. The exchange illustrates how a diplomatic dispute can become a kitchen-table issue involving jobs, prices and the financial security of communities on both sides of the border.

The Next Test Is Whether Trade Pressure or Legal Restraint Prevails

The warning leaves Ottawa with no simple option. Rolling back tariffs could reduce costs for Canadian businesses and consumers while potentially depriving the White House of evidence supporting its discrimination allegations. However, doing so could also mean surrendering an important bargaining tool before Washington offers meaningful concessions. Maintaining the tariffs preserves Canada’s ability to apply economic pressure, but it also risks prolonging higher costs and complicating some American legal challenges. Neither approach guarantees success. Ultimately, U.S. courts would need to decide whether Section 338 remains legally available, whether the necessary evidence of discrimination exists and whether Trump’s actions fall within the authority Congress granted.

Diplomacy remains equally uncertain. Washington declined to renew CUSMA in its existing form during the July 2026 review, although the agreement remains in force. As recently as October 1, U.S. Trade Representative Jamieson Greer acknowledged that several difficult issues remained unresolved despite continuing technical discussions with Canada. The MEI’s warning therefore highlights a broader strategic dilemma: whether Ottawa should prioritize immediate retaliation or place greater emphasis on legal challenges, negotiations and trade diversification. For manufacturers planning investments and families confronting higher prices, the outcome carries real consequences. Retaliatory tariffs can demonstrate resolve, but ending an entrenched trade war may require a strategy that succeeds at the negotiating table without weakening Canada’s position in court.

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